Science, Week 21

Environmental Science 5
Lesson 21
LIFE SCIENCE
The study of life involves answering the question "Is it alive?" Living organisms all share five certain characteristics. Some of these are common sense, and some are a little less obvious. All living things are made up of one or more cells. Your body contains trillions of cells, while some organisms have only one cell! The cell "organizes" life. That is the cell's number one job! All living things use energy to grow. This is called "metabolism." Since all living things must eventually die, they all have a process to ensure that "life goes on." This is called reproduction. All living things maintain their own internal environment. This process of staying stable is called homeostasis, which comes from the Latin homeo, meaning the same, and stasis, meaning staying. A fish in water doesn't turn into water, but keeps its own shape. Mammals maintain their 98.6 degrees Fahrenheit body temperature even when it is freezing cold outside. These are examples of homeostasis. Another amazing thing about living organisms is that their offspring look like their parents! This is called heredity.
There are other things that living organisms do, but they don't "define life." Most animals move, but some animals, and lots of plants, do not. Some things that are not living move, like water and clouds. Animals and plants respond to things in their environment. Plants grow toward the light, and animals shiver when the air is cold. All living things develop, growing from single cells to mighty oak trees or a 2,000 pound bull moose, and then they die. These organisms are complex, with even small bacteria having many different structures within them. However, there are many non-living things that are complex, like your parents' car engine! So, while these characteristics are important, they are shared with many non-living things.

1. Gather the following things together (or come up with your own list), and place them on a table: Apple, pencil, house plant, worm (place in a jar with some earth), rock, glass of water from the tap, glass of water from a pond, a leaf. Write down the five characteristics for life listed above. Classify each item as either LIVING or NON-LIVING, and explain how you decided on the classification.
OH MY GOD! YOU THINK EVERYTHING KEEPS SLIPPING FROM MY MIND, DON’T YOU?! WELL… I WAS LEARNING THIS WHEN I WAS FOUR! “WOW, I NEVER KNEW THAT ROCKS WEREN’T ALIVE!” AUGH! Fine Mom, rocks DO NOT: Grow, change, or breathe.


Let's get down to basics and look at the building blocks for plants and animals - CELLS! Your body is made up of trillions of cells. They are so small that you need a microscope to see them. To be specific, your body contains about 100 trillion cells. That is the number one, with 17 zeroes after it! If your cells were the size of hamburgers, they would make a wall 13 feet high, one foot wide, and long enough to wrap all the way around the Earth. We all start as one cell, a fertilized egg. To get to trillions of cells, that cell divides. This process is called mitosis, or cell division. In this process, genetic material (DNA and RNA) is passed on. Cells divide to make new cells and then die continuously. Whoops - except for brain cells! We are born with a certain number of brain cells, and don't make any more (although some scientists are beginning to question this). Take good care of the ones you have.
Cells are specialized for each job that they perform. For example, nerve cells carry messages to the brain, muscle cells contract and relax so that we can move, and red blood cells carry oxygen thoughout the body. For cells to do all of these jobs, they need energy. The main source of energy is glucose. The process of turning glucose (along with oxygen) into energy (and water) is called metabolism. It takes a lot of "teamwork" on the part of our cells to get us through the day. Groups of cells get together and form organs - stomach, heart, lungs. Groups of organs work together to get the job done - mouth, esophagus, stomach and intestines do the job of digesting food. This is called an organ system; in this case the digestive system.
Now we will zoom in on some cells. There are some basic parts to a cell, but not all cells have every part. Viruses don't even have cells! They just have the information for reproduction (DNA or RNA) inside of a protein coat. Plant and animal cells are different from each other. Plant cells have cell walls, and chloroplasts, which animal cells don't have. The vacuoles in plant cells are also much bigger than those in animal cells.
Let's start on the outside of an animal cell (remember, plant and animal cells are different). Animal cells are surrounded by a cell membrane. The Latin word membrana means "skin." This soft layer around the cell holds everything together, and makes sure nothing goes in or out that isn't supposed to. Food and water can pass through the cell membrane.
Inside of this membrane, the organelles float around in a jelly-like substance called cytoplasm. It is made up of water, salt and enzymes. It is thought that the cytoplasm helps the cell to move, and it keeps all of the other organelles separated from each other.
Inside the cell are various organelles that each have different jobs. An organelle is a specialized part of a cell that acts like an organ in the body. The biggest and most noticeable organelle in the cell is the nucleus. This is the "control center" of the cell, or the director of all of the activities in the cell. The nucleus is surrounded by a nuclear envelope which will only allow two things to move through: proteins for energy, and the heredity information in the RNA.
Inside of the nucleus is the nucleolus. It is the dark spot that you see in a picture of a nuclueus, and it contains just protein and RNA, with a little bit of DNA thrown in. The nucleolus produces ribosomes.
There are a lot of ribosomes in a cell, as many as a few million! These organelles make proteins. Some of these proteins will be used inside the cell, and these are made by "floating" ribosomes. Other proteins will be sent outside the cell, and these are made by ribosomes attached to the endoplasmic reticulum.
There are two kinds of endoplasmic reticulum ("ER"). These are the rough and the smooth ER. The rough ER is covered with bumps, which are the ribosomes. This organelle makes proteins and creates a bubble, or vesicle around them. These proteins are then moved to the Golgi apparatus for use inside of the cell, or to the cell membrane to be used outside of the cell. The smooth ER collects and contains proteins and ions for later use. It can also detoxify poisons.
The Golgi apparatus is a little tricky to say. It is pronounced "gol-gee apparatus." It looks kind of like a stack of puffy pancakes. The Golgi apparatus combines simple molecules into bigger molecules. It also produces lysosomes.
lysosomes contain digestive enzymes, surrounded by a single membrane. The word lysosome comes from lyso, meaning to break down or digest, and some, meaning body. So, these organelles break down bigger molecules. If the lysosome were to explode, the cell itself would break down.
The mitochondria are the "powerhouse" of the cell. They act like a furnace, in that they break down food and release energy, or "food" for the cell. The mitochondria is shaped like a sausage. If you were to look inside this organelle, you would see the inner membrane all folded up like a maze. These folds create more surface area, which gives the mitochondria more "room" to release energy. Even though the mitochondria are small, they are the second largest organelle in the cell. Depending on how much energy the cell needs, there may be hundreds or thousands of them.
The other organelle that you would see looking at a cell is the vacuole. These are "bubbles" that float in the cell, and store various things that the cell needs. Some store food, and others store waste. Vacuoles are very important to plant cells, too. In plants the vacuole takes up about half of the cell. In poisonous plants, vacuoles store the poisonous chemical that the plant produces to keep herbivores from eating it. The poison is released only when the cell is bitten into or swallowed.

1. Go to this website and read more about cells. Draw an animal cell and a plant cell. Label all of the organelles.


2. The Edible Cell:
Mix up Jell-O from directions on the box.
Cool to room temperature and pour into a Zip-loc plastic bag.
Add fruits and candies to represent the organelles. For example, an orange slice for the mitochondria; a cherry for the nucleus; string licorice for microtubules, etc.
Close the bag. Make a legend, writing down which organelle each piece of fruit represents.
Put the bag in the refrigerator and allow the Jell-O to get firm.
Eat the cell!

In plants, vacuoles are very big. These vacuoles hold lots of water for the plant, or food, or waste. When a plant has lots of water, the vacuoles are full, and the plant stands tall (with the help of the cell wall). As the plant loses water in a drought, the vacuoles shrink, and the plant begins to droop. If you give the plant water, the vacuoles fill up, and the plant stands straight again.
The cell wall in plants is similar to the cell membrane in animals. It regulates what goes in and out of the plant cell. It is made of a substance called cellulose.
Plant cells also have chloroplasts, which is where they create food using energy from the sun. Chloroplasts are complex green structures which give plants their color. They are not present in fungi, because these plants do not produce their own food. There are other pigments in leaves, and when the chlorophyll disappears from the leaves in the fall, these show up as beautiful reds and yellows.

3. Click here to go to a printable table comparing plant and animal cells. Print out the table, and fill in the blanks.


4. Click here to look at some real pictures of cells. Write a sentence telling what each cell reminds you of.
The Vitamin C looks like some strange 3D graphics mess-up.
The Staphylococcus looks like some orange grapes.
The Leukemia looks like an amoeba.
The blood clot looks like glue combined with sticky hair.
The E. coli looks like some strange radio scan of something.
The Strepto—whatever looks like a blob of neurotic cells.
The red blood cells look like half-sucked, red cough drops.
The soil bacteria look like green rice.
The eosinophil looks like a plant with it’s roots.
The neutrophils looks like the cross section of a worm.